A₈Tl₁₁ (A= alkali metal) compounds have been known since the investigations of Corbett et al. in 1995^[1] and still are matter of current discussions as the compound includes one extra electron referred to the charge of the Tl₁₁⁷⁻ cluster. Attempts to substitute the charge by incorporation of a halide succeeded for the lightest homologue of the group, Cs₈Ga₁₁Cl, and powder diffraction experiments for the heavier homologues also suggested the formation of analogous compounds. ^[2] However, X-Ray single crystal studies on A₈Tl₁₁X to prove this substitution and to provide a deeper insight into the influence on the thallide substructure have not yet been performed, probably due to severe absorption combined with air and moisture sensitivity for this class of compounds. In our contribution we present single crystal X-Ray analyses of the new compounds Cs₈Tl₁₁Cl_0.8, Cs₈Tl₁₁Br_0.9 and Cs₅Rb₃Tl₁₁Cl_0.5. It is shown that a (partial) incorporation of halide can also be indirectly determined by examination of the Tl-Tl distances for low resolved data sets, e.g. for Cs_5.7K_2.3Tl₁₁Cl_?. Mixed occupied sites by two different alkali metals indicate a dependence on the cesium content, the systems K/Rb – Tl – Br and K/Rb – Tl – Cl only gave rise to the formation of the higher reduced (K/Rb)₈Tl₁₁ and the less reduced by-product (K/Rb)₁₅Tl₂₇. We have not been able to prove the formation of halide including thallides in the absence of cesium.

[1] Z. C. Dong, J. D. Corbett, J. Cluster Sci. 1995, 6, 187-201.

[2] R. W. Henning, J. D. Corbett, Inorg. Chem. 1997, 36, 6045-6049.